Optical discs, which are a kind of optical recording media, can record a large amount of data, and are now being widely used. Currently, a kind of innovative high-density digital versatile disc (HD-DVD) such as blue ray disc (Blu-ray Disc) is under development. This kind of medium can record and store video data of high quality and audio data of high fidelity for a long time.
The Blu-ray disc is a next generation optical recording solution that can store a larger amount of data than a conventional DVD.
The Blu-ray disc generally employs a blue-violet laser having a wavelength of 405 nm. This wavelength is shorter than a red laser used on a conventional DVD. The wavelength of the red laser is 650 nm. The Blu-ray disc has a thickness of 1.2 mm and a diameter of 12 cm, and includes a light transmission layer having a thickness of about 0.1 mm. Therefore, the Blu-ray disc can store a larger amount of data than a conventional DVD.
An optical disc device for writing and reading data on the Blu-ray disc is shown in FIG. 1. It includes an optical pick-up 11 for writing and reading a signal to and from an optical disc 10, a video disc recorder (VDR) system 12 for processing the signal read out from the optical pick-up 11 into a replay signal, or for modulating and processing an externally inputted data stream into a record signal suitable for recording, and an encoder 13 for encoding an externally inputted analog signal and outputting the encoded analog signal to the VDR system 12.
A Blu-ray disc can be of a rewritable type, which is referred to herein as a Blu-ray Disc Rewritable (BD-RE). A BD-RE has a rewritable capability, which enables video and audio data to be written, erased, and rewritten thereon repeatedly.
The BD-RE, as shown in FIG. 2 is divided into a lead-in area (LIA), a data area and a lead-out area (LOA), and the front and the rear of the data area are allocated to have an inner spare area (ISA) and an outer spare area (OSA).
With the BD-RE configured in the manner described above, the VDR system 12 of the optical disc device shown in FIG. 1 encodes and modulates externally inputted data into a signal suitable for recording, and records by cluster unit corresponding to error correction block unit. If a defective area occurs in the data area while recording data on the BD-RE, the data of one cluster unit recorded on the defective area is also recorded on the spare area (for example, the inner spare area on the BD-RE) according to a linear replacement operation. A series of linear replacement operations can be performed.
Accordingly, the VDR system 12 of the optical disc device records the data of the cluster unit recorded on the defective area onto the spare area, even if the defective area occurs in the data area of the rewritable Blu-ray disc. When a playback operation is performed for the rewritable Blu-ray disc, the data recorded onto the spare area are read out and replayed so that a data recording error can be prevented.
Various standards related to the Blu-ray disc are under development.
In this respect, a second type of Blu-ray disc, on which data is not repeatedly rewritten (non-rewritable), but is written only once, is herein referred to as a Blu-ray Disc Write-Once (BD-WO). The Write-once Blu-Ray disc is useful when it is not desirable to repeatedly rewrite data. In a BD-WO, management of defective areas is needed.
But since data can be recorded on the BD-RE repeatedly (due to the characteristics of the BD-RE), the size of the defect management area (DMA) for the rewritable Blu-ray disc is relatively small (see DMA 1˜DMA 4 in FIG. 2). In contrast, since data is recorded on the write-once Blu-ray disc only one time, the area required in the BD-WO to manage the defective area needs to be larger than the area required for a write-once Blu-ray disc. Accordingly, a sufficiently sized defect management area should be allocated for the BD-WO.
A Blu-ray disc such as a BD-WO having both a sufficiently sized defect management area can store an even greater amount of data than the conventional DVD when a cross-section two-layers recording technology is applied for making two recording layers on one side of the disc with 0.85 NA (Lens Numerical Apertures). An increase in storing capacity is achieved by closely irradiating rays being passed through a lens to the optical disc.
A Blu-ray disc has generally a high numerical aperture lens, increased density, and a 0.32 μm track pitch. An optical disc being manufactured by using the Blu-ray disc technology can transmit data at a much faster speed than a DVD ROM and a CD ROM. When formatting video and audio data, a formatting method being presently used for DVD such as MPEG2 (video), AC3, MPEG1 and layer 2 (audio) should be used so as to maintain compatibility with the conventional methods. A feature of a HD-DVD type drive (such as BD-WO) effectively protecting data, should be such that its data can be stored on and reproduced from most of conventional DVD discs being presently used.